PETROLOGICAL ABSTRACTS AND REVIEWS 403 



5. Second period of volcanic eruption, with subsequent erosion. 



4. Uplift and erosion of (3). 



3. Subsidence and deposition of limes, sands, and clays. 



2. Andesitic lavas extruded, later eroded. 



I. Plutonic intrusives, eroded to late maturity. 



The first part of the paper describes the general geology of the islands; the 

 foregoing is a brief summary. The second part discusses the petrography of 

 the region studied. The important sediments are chiefly calcareous, but some 

 conglomerate is known — river gravel, with bowlders of all sorts, and a calcar- 

 eous conglomerate with over 50 per cent igneous bowlders but much shell-waste 

 in the cement. The igneous rocks described are chiefly andesites and basalts, 

 of which the latter preponderate in the descriptions. 



Some of the extrusions were submarine, marked generally by the presence 

 of hornblende; this character almost appears to be diagnostic of the subaqueous 

 origin of such flows as bear it. Another interesting feature is the persistent 

 association of hypersthene and hornblende. 



The first andesitic period is recognized only on the two large islands. The 

 flows of the second andesitic period are widespread and may be essentially 

 synchronous in origin with some basalts and rhyolites. The lavas of the 

 basaltic period, again, are more limited in their distribution. In general, 

 differentiation in Fiji progressed from acid to basic. Volcanic vents have been 

 singularly persistent, the basaltic flows seldom or never forming cones of their 

 own. Ten rock analyses are presented, but no modes are given and only a few 

 of the rocks are classified according to the norm system. 



GoLDSCHMiDT, V. M. Die Gesetze der Gesteinsmetamorphose, mit 

 Beispielen aus der Geologie des SUdlichen Norwegens. Christi- 

 ania, 1912. Pp. 16, fig. i. 



A concise application of the laws of thermodynamics to metamorphism. 

 The "mineralogical phase rule" states that in a stable combination as many 

 minerals may be formed as there are variables in the system. Thus in a mix- 

 ture of silica, magnesia, and alumina only three minerals may be developed. 

 The conditioning agents in contact metamorphism are pressure and tempera- 

 ture. By plotting the pressure horizontally and the temperature vertically, 

 various fields are obtained which are either gradational or sharply marked off 

 from each other. The melting temperatures of the more refractory minerals 

 limit the phase-curve above. The effect of pressure is well illustrated by 

 grossularite, which requires a higher pressuie to maintain its identity at high 

 temperatures than at low ones; its compact atomic structure is also favorable 

 to stabihty at high pressures. Separate curves for each system may be pre- 

 pared by applying the third principle of thermodynamics, Nernst's theorem; 

 the approximate formula used in calculating the curve is from the same inves- 

 tigator. Such a curve applied to the system CaO.SiO2.CO2 yields a change 



